Area codes 450, 579, and 354 are telephone area codes in the North American Numbering Plan in the Canadian province of Quebec, encompassing the off-island suburbs of Montreal, as well as the rest of the Montérégie region southward to the border with New York state. Among the cities in the numbering plan area are Laval, Longueuil, Terrebonne, Saint-Jean-sur-Richelieu, Brossard, Repentigny, Saint-Jérôme, Granby, Blainville and Saint-Hyacinthe.

Area code 450 is also shared by several small communities in an adjacent part of Ontario: some landline customers in Chute-à-Blondeau (East Hawkesbury), near Pointe-Fortune use numbers from the Rigaud exchange 451.

Area code 514 served the entire Montreal area for over half-a-century. However, by the mid-1990s, it was on the verge of exhaustion because of Montreal's rapid growth and Canada's inefficient system of number allocation. All competitive local exchange carriers in Canada are allocated blocks of 10,000 numbers for every rate centre in which they plan to offer service, even in the smallest hamlets. Even though most rate centres do not need nearly that many numbers, a number cannot be reallocated elsewhere once it is assigned to a carrier and rate centre. That resulted in thousands of wasted numbers. By the late 20th century, that made a second area code necessary in Canada's second-largest toll-free calling zone.

Area code 450 entered service in 1998. The numbering plan area completely surrounds area code 514, which was confined to the Island of Montreal and a few surrounding islands, and so it is one of the six pairs of "doughnut area codes" in the numbering plan, and the only one in Canada (Toronto's area code 416 also borders Lake Ontario). For that reason, Montrealers sometimes refer to the off-island suburbs as "les 450" (the 450s), much like the suburbs of Toronto are called "the 905."

On May 7, 2009, the CRTC ruled that area code 438, which had been used as an overlay for area code 514 since 2006, would be extended to overlay area codes 450 and 514.^[1] However, a later decision changed that to overlay only area code 450 with the new area code 579, effective August 21, 2010.^[2]

On May 2, 2011, a prepaid mobile telephone registered to "Pierre Poutine, Separatist Street, Joliette," at (450) 760-7746 on Bell Mobility's "Virgin" service played a key role in a robocall scandal in which voters in Guelph, Ontario were inundated with calls directing them to the wrong polling station.^[3][4]

Area code 354 was formally assigned as of February 2, 2019 as an additional area code for the 450/579 overlay complex,^[5] but the relief action was suspended indefinitely on October 8, 2019, and that area code is now in use since October 22, 2022.^[6]

The incumbent local exchange carrier (ILEC) for the 450, 579 and 354 territory is Bell Canada. The major competitive local exchange carriers (CLECs) are Vidéotron and Telus.

• List of NANP area codes
• North American Numbering Plan

• CNA exchange list for area +1-450
• CNA exchange list for area +1-579
• Telecom archives
• Area Code Map of Canada

45°37′N 73°56′W / 45.61°N 73.94°W / 45.61; -73.94